The invention is generally in the field of ultrasound measurement techniques, and relates to an ultrasonic transducer probe for measuring the biological fluid flow within a vessel, and a measurement device utilizing such a probe. The invention is particularly useful for Doppler-based blood flow measurement and the determination of associated hemodynamic parameters.
Ultrasonic probes are typically used for non-invasive measurements. When dealing with moving objects, such as blood in a patient""s body, Doppler-based measurement techniques are typically used. These measurement techniques are generally of two types, utilizing, respectively, continuous and pulse transmission of ultrasonic waves.
U.S. Pat. No. 4,370,985 discloses a Doppler based ultrasound probe device for measuring blood flow rate and blood vessel diameter utilizing the continuous transmission of ultrasonic waves.
EP 0150672 discloses a process and device for determining the velocity and rate of flow of a fluid in a pipe by using a Doppler echographic method. Here, two mutually attached wave-train transmitter-receiver units are used and oriented with respect to a pipe such that the axis of one of the units is perpendicular to the axis of the pipe.
U.S. Pat. No. 4,103,679 discloses a Doppler based ultrasound system for blood flow measurement in a blood vessel. In this system, an ultrasound transducer array is used, being disposed relative to the blood vessel""s longitudinal axis such that a pulse wave ultrasound beam emanating therefrom intercepts the blood vessel""s longitudinal axis at a variable beam inclination angle xcex8. By this, blood flow can be quantitatively measured, independent of the beam inclination angle.
Other pulse-transmission based techniques are disclosed in the following publications: xe2x80x9cNew, Angle-independent, Low-Cost Doppler System to Measure Blood Flowxe2x80x9d by M. Skladany et al., The American Journal of Surgery, Volume 176, August 1998, pgs. 179-182; and WO 97/24986.
Another technique based on the transmission of pulses of two ultrasound waves aimed at determining blood velocity is disclosed in WO 97/24986. This technique is based on the zero-crossing method for frequency measurement of Doppler shifts and the use of FM modulated or pulse signals with range clipping for localizing velocity measurements.
There is a need in the art to facilitate ultrasonic-based blood flow measurements by providing a novel probe device and a measuring device using the same.
The main idea of the present invention consists of providing a probe device of a specific design, which assists in orienting the probe device with respect to the blood vessel under measurement and in operating the probe device during measurement, and facilitates access of the ultrasound radiation to the blood vessel under measurement.
An ultrasonic probe device according to the invention is characterized by that an outer surface of the device, by which it is brought into contact with the patient""s body, is patterned so as to have at least one projecting portion. A single tip-like projecting portion may be provided. This enables to manipulate the probe with respect to the patient""s body so as to displace a muscle above the blood vessel, thereby minimizing ultrasound signal attenuation during measurements, and also to bring the transducer arrangement closer to the blood vessel.
The pattern may be in the form of two spaced-apart projections defining a recess (groove) therebetween. By using such a probe for measurements during a surgical operation (i.e., in a direct contact with a blood vessel under measurements), the blood vessel may be located within the recess, thereby stabilizing the measurements. The provision of such a recess-containing pattern also facilitates non-invasive measurements, for example, for dialysis grafts.
The probe dice may have a housing of a single-part design, or of a two-part design. In the case of the two-part design, one part is removably mountable onto the other part, and the pattern is formed on an outer surface of the removable part (by which the probe is brought into contact with tie patient""s body). When the projection-recess pattern is made on the outer surface of the removable part of the housing, this part actually presents an adapter between the probe and the blood vessel. Various adapters with various pattern dimensions may be prepared, thereby enabling to select a suitable one to be mounted onto the transducers containing part of the housing.
A measurement device according to the invention for ultrasound-based blood flow measurements is characterized by that a probe unit and a control unit of the device are located adjacent to each other, the device thereby being a portable hand-held measurement device. Preferably, the probe unit and the control unit are incorporated in a common housing, e.g., shaped so as to be held like a pen. The control unit comprises probe operation means and indication means for generating signals indicative of the measurement results. The control unit may comprise a display, and/or a data processing and analyzing utility. Alternatively, or additionally, the measurement device is connectable to an external unit, having a display and/or such a data processing and analyzing utility. This design of the measurement device aids a user (physician) in monitoring and analyzing data during the measurements, and, if the above design of the probe is used, in orienting the probe along the longitudinal axis of the blood vessel under measurements.
There is thus provided, according to one aspect of the present invention, a probe device for use in an ultrasound measurement device, the probe device comprising a housing containing a transducer arrangement, an outer surface of the housing, by which it is brought into contact with the patient""s body during operation, being patterned so as to have at least one projecting portion.
Preferably, the transducer arrangement comprises two transducers, each operating in transmitting and receiving modes. The transducers are preferably oriented with respect to each other such that first and second ultrasound beams produced by the first and second transducers, respectively, propagate along first and second beam propagation axes intersecting at a certain acute angle. Preferably, during the measurements, the probe is desirably positioned with respect to the blood vessel, such that each of the beam propagation axes intercepts the longitudinal axis of the blood vessel. This can be implemented by displacing the transducers with respect to the blood vessel, and performing preliminary measurements of the blood vessel diameter.
According to another aspect of the present invention, there is provided an ultrasonic transducer probe device for use in a measurement device for blood flow measurements in a patient""s body, wherein:
the probe device comprises a housing containing a transducer arrangement;
an outer surface of the housing, by which it is brought to a measurement location in the patient""s body, is patterned so as to have at least one projecting portion;
said transducer arrangement comprises first and second ultrasonic transducers, each operable in transmitting and receiving modes, the first and second transducers being oriented with respect to each other such that first and second ultrasound beams produced by the first and second transducers, respectively, propagate along first and second beam propagation axes intersecting at a certain acute angle.
According to yet another aspect of the present invention, there is provided an ultrasonic transducer probe device for use in a measurement device for non-invasive blood flow measurements in a patient""s body, wherein:
the probe device comprises a housing containing a transducer arrangement;
an outer surface of the housing, by which the probe is brought into contact with the patient""s body, is patterned so as to have a projecting tip-like portion, which, during manipulation of the probe with respect to the patient""s body, enables to displace a muscle above a blood vessel under measurements.
According to yet another aspect of the present invention, there is provided an ultrasonic transducer probe device for use in a measurement device for non-invasive blood flow measurements in a patient""s body, wherein:
the probe comprises a housing containing a transducer arrangement,
an outer surface of the housing, by which the probe is brought into contact with the patient""s body, is patterned so as to have a projecting tip-like portion, which, during manipulation of the probe device with respect to the patient""s body, enables to displace a muscle above a blood vessel under measurements;
the transducer arrangement comprises first and second ultrasound transducers, each operable in transmitting and receiving modes, the first and second transducers being oriented with respect to each other such that first and second ultrasound beams produced by the first and second transducers, respectively, propagate along first and second beam propagation axes intersecting at a certain acute angle;
According to yet another aspect of the present invention, there is provided a probe device for use in an ultrasound measurement device for measuring a blood flow condition in a patient""s blood vessel, wherein:
the probe comprises a housing containing a transducer arrangement;
the housing is composed of first and second parts, the second part being removably mountable onto the first part, an outer surface of said second part, by which the probe is brought into contact with the blood vessel during measurements, having a pattern defining a recess for locating the blood vessel therein.
According to yet another aspect of the present invention, there is provided a probe device for use in an ultrasound measurement device for measuring a blood flow condition in a patient""s blood vessel, wherein:
the probe comprises a housing containing a transducer arrangement;
the housing is composed of first and second parts, the second part being removably mountable onto the first part, an outer surface of said second part, by which the probe is brought into contact with the blood vessel during measurements, having a pattern defining a recess for locating the blood vessel therein;
said transducer arrangement comprises first and second ultrasonic transducers, each operable in transmitting and receiving modes, the first and second transducers being oriented with respect to each other such that first and second ultrasound beams produced by the first and second transducers, respectively, propagate along first and second beam propagation axes intersecting at a certain acute angle.
In a measurement device according to the invention, the probe device and a control unit are located adjacent to each other, preferably being incorporated in a common pen-like housing. The control unit comprises at least an operation means for operating the probe device (including user""s interface, e.g., keys, and electronic components), and an indication means, and may also comprise a display and/or data processing and analyzing utility. By this, a user (physician) can use the probe in the most convenient manner (without a need to move his eyes away from the measurement site).
Thus, according to yet another aspect of the present invention, there is provided a hand-held measurement device for ultrasound-based measurements of a blood flow in a patient""s body, the device comprising an ultrasonic transducer probe device and a control unit accommodated in a common housing, the control unit comprising an operation means for operating the probe and an indication means for generating data indicative of measurement results.
A preferred measurement technique consists of the following: once the probe is desirably positioned, measurements are carried out consisting of insonating the blood vessel with two pulse-wave ultrasound beams, in a manner to substantially simultaneously (in comparison to the physiological time scale) obtain multiple sample volumes at successive coordinates (gates) along each of the beam propagation axes. In other words, for each of the beams, the reflection amplitude with Doppler shifted frequency is measured as a function of sample volume position along the ultrasound beam axis, and is represented in the sampled form as an n-element vector where the i-th element is an instantaneous value of reflection amplitude for a particular gate. By applying the complex demodulation technique, which utilizes the synchronous multiplication of this real vector of reflection amplitudes on two periodic functions with 90xc2x0-shift in phase and with the frequency equal to that of the transmitted radiation, and applying a low pass filtering, the n-element vector of complex values (I and Q) for each of the beam is obtained. By this, the central spectral frequency of the complex vector is shifted from that of the ultrasound pulse towards zero frequency. By repeating the ultrasound pulses transmission/receiving procedure m times, an nxc3x97m two-dimensional matrix Eij of reflection amplitude values is obtained for each of the beams. Here, i is the gate coordinate index (i=1, . . . ,n) and j is the time coordinate index (j=1, . . . ,m). It should be understood that each of the reflection amplitude values is complex and indicative of the amplitude and the phase of the reflection at the respective gate at a certain time. By processing and analyzing these matrices (for two beams), the diameter of the blood vessel can be calculated, as well as the dynamic characteristics of the blood flow, such as Doppler shifts, inclination angles, velocity, and velocity profile along the ultrasound beam.